Plastic pipe insertions in steel gas service lines have, for the last number of years, come into widespread use. When a steel gas service line corrodes, the replacement thereof involves the complete excavation of all earth over the steel service line with the subsequent replacement of the line with a new line. This procedure has obvious drawbacks. A common expedient for repairing steel service lines without extensive excavation is to insert a plastic tube or plastic conduit into the existing line. In utilizing insertion, it is necessary to dig a hole at the gas main in order to attach the plastic tube or pipe to the main in a gastight connection. For this purpose the existing metallic pipe is cut at the main and the plastic pipe (which is inserted through the existing metallic pipe) is attached to the tee in a gastight manner. This operation requires digging a hole at the main in order to be able to expose the tee.
Where the main is located under a street or under a sidewalk (as in city areas), the hole digging process is quite costly and results in a considerable amount of excavation.
In view of the objectionable nature of the excavation at the main, it has been found to be desirable to effect a plastic insertion that does not require digging at the tee. More particularly, it has been found that the vast majority of leaks in existing service lines occur not at the tee but rather at a point somewhere along the existing metallic service line. This being the case, it is possible to be able to insert a plastic tube into an existing metallic service line from the building (where the pipe enters the building) and, thereafter, effect a seal at the remote end of the service line using remote sealing techniques.
Insertion devices adapted to be placed into existing service lines from the building are termed "no-hole" devices for the reason that there is no necessity for excavating or digging at the tee. One example of a prior art no-hole insertion device is shown in the U.S. Pat. No. 4,166,479 to Cleavenger.
The principal problem encountered in no-hole insertion devices is the establishment of a fluid tight joint and seal inside the existing service line near the tee. Since the tee is located, in many instances, 50-100 feet from the building foundation, remote sealing techniques are necessary in order to provide for establishment of a fluid tight joint and seal after insertion. Prior art remote sealing structures and methods have been known to produce, in many instances, unsatisfactory results. Corrosion problems, seal deterioration and pull-out, are all problems that are characteristic of one or more prior art devices and which have limited the acceptability of no-hole insertion devices in the gas industry.
The apparatus and structure of this invention overcome many of the problems associated with prior art devices and methods in providing for the placement and establishment of a fluid tight joint and seal in a no-hole insertion structure.